Under the current Local Autonomy Law, each prefecture is subdivided into cities (市,shi?) and districts (郡,gun?) and each district into towns (町,chō/machi?) and villages (村,son/mura?). For example, Hokkaido has 14 subprefectures that act as branch offices (支庁,shichō?) of the prefecture. Some other prefectures also have branch offices that carry out prefectural administrative functions outside the capital. Tokyo, the capital of Japan, is a merged city-prefecture; a metropolis, it has features of both cities and prefectures.

The West's use of "prefecture" to label these Japanese regions stems from 16th-century Portuguese explorers' and traders' use of "prefeitura" to describe the fiefdoms they encountered there. Its original sense in Portuguese, however, was closer to "municipality" than "province". (Today, in turn, Japan uses its word ken (県), meaning "prefecture", to identify Portuguese districts while in Brazil the word "Prefeitura" is used to refer to a City Hall.)

Those fiefs were headed by a local warlord or family. Though the fiefs have long since been dismantled, merged, and reorganized multiple times, and been granted legislative governance and oversight, the rough translation stuck.

The Meiji government established the current system in July 1871 with the abolition of the han system and establishment of the prefecture system (廃藩置県 haihan-chiken). Although there were initially over 300 prefectures, many of them being former han territories, this number was reduced to 72 in the latter part of 1871, and 47 in 1888. The Local Autonomy Law of 1947 gave more political power to prefectures, and installed prefectural governors and parliaments.

In 2003, then-Prime MinisterJunichiro Koizumi proposed that the government consolidate the current prefectures into about 10 regional states. The plan called for each region to have greater autonomy than existing prefectures. This process would reduce the number of sub-prefecture administrative regions and cut administrative costs.[2] The Japanese government is also considering a plan to merge several groups of prefectures, creating a sub-national administrative division system consisting of between nine and 13 states, and giving these states more local autonomy than the prefectures currently enjoy.[3] As of August 2012[update], no reorganization has been scheduled.

Historically, during the Edo period, the Tokugawa shogunate established bugyō-ruled zones (奉行支配地) around the nine largest cities in Japan, and 302 township-ruled zones (郡代支配地) elsewhere. When the Meiji government began to create the prefectural system in 1868, the nine bugyō-ruled zones became fu (府), while the township-ruled zones and the rest of the bugyo-ruled zones became ken (県). Later, in 1871, the government designated Tokyo, Osaka, and Kyoto as fu, and relegated the other fu to the status of ken. During World War II, in 1943, Tokyo became a to, a new type of pseudo-prefecture.

Despite the differences in terminology, there is little functional difference between the four types of local governments. The sub-national governments are sometimes collectively referred to as to-dō-fu-ken(都道府県?) in Japanese, which is a simple combination of the four terms.

Tokyo is referred to as to (都), which is often translated as "metropolis." The Japanese government translates Tōkyō-to as "Tokyo Metropolis" in almost all cases, and the government is officially called the "Tokyo Metropolitan Government". But there are some people who call Tōkyō-to "Tokyo Prefecture" in English.

Following the abolition of the han system, Tōkyō-fu (an urban prefecture like Kyoto and Osaka) encompassed a number of cities, the largest of which was Tokyo City. Tokyo City was divided into 15 wards. In 1943, Tokyo City was abolished, Tōkyō-fu became Tōkyō-to, and Tokyo's wards became the special wards, local authorities falling directly under the prefecture in hierarchy, each with their own elected assemblies (kugikai) and mayors (kuchō). A number of suburban villages and towns were converted to wards, bringing the total number of special wards to 35. The reorganization's aim was to consolidate the administration of the area around the capital by eliminating the extra level of authority in Tokyo. The central government wanted to have greater control over Tokyo due to Japan's deteriorating position in World War II and the possibility of emergency in the metropolis.

After the war, Japan was forced to decentralize Tokyo again, following the general terms of democratization outlined in the Potsdam Declaration. Many of Tokyo's special governmental characteristics disappeared during this time, and the wards took on an increasingly municipal status in the decades following the surrender. Administratively, today's special wards are almost indistinguishable from other municipalities.

The postwar reforms also changed the map of Tokyo significantly: In 1947, the 35 wards were reorganized into the 23 special wards, because[citation needed] many of its citizens had either died during the war, left the city, or been drafted and didn't return.

There are some differences in terminology between Tokyo and other prefectures: police and fire departments are called chō (庁) instead of honbu (本部), for instance. But the only functional difference between Tōkyō-to and other prefectures is that Tokyo administers wards as well as cities. Today, since the special wards have almost the same degree of independence as Japanese cities, the difference in administration between Tokyo and other prefectures is fairly minor.

Hokkaido is referred to as a dō (道) or circuit. This term was originally used to refer to Japanese regions consisting of several provinces (e.g. the Tōkaidō east-coast region, and Saikaido west-coast region). This was also a historical usage of the character in China. (In Korea, this historical usage is still used today and was kept during the period of Japanese rule.)

Hokkaido, the only remaining dō today, was not one of the original seven dō (it was known as Ezo in the pre-modern era). Its current name is believed to originate from Matsuura Takeshiro, an early Japanese explorer of the island. Since Hokkaido did not fit into the existing dō classifications, a new dō was created to cover it.

The Meiji government originally classified Hokkaido as a "Settlement Envoyship" (開拓使 kaitakushi), and later divided the island into three prefectures (Sapporo, Hakodate, and Nemuro). These were consolidated into a single Hokkaido Department (北海道庁 Hokkaido-chō) in 1886, at prefectural level but organized more along the lines of a territory. In 1947, the department was dissolved, and Hokkaido became a full-fledged prefecture. The -ken suffix was never added to its name, so the -dō suffix came to be understood to mean "prefecture."

When Hokkaido was incorporated, transportation on the island was still underdeveloped, so the prefecture was split into several "sub-prefectures" (支庁 shichō) that could fulfill administrative duties of the prefectural government and keep tight control over the developing island. These sub-prefectures still exist today, although they have much less power than they possessed before and during World War II: they now exist primarily to handle paperwork and other bureaucratic functions.

"Hokkaido Prefecture" is, technically speaking, a redundant term, although it is occasionally used to differentiate the government from the island itself. The prefecture's government calls itself the "Hokkaido Government" rather than the "Hokkaido Prefectural Government".

Osaka and Kyoto Prefectures are referred to as fu (府). The Classical Chinese character from which this is derived implies a core urban zone of national importance. Before World War II, different laws applied to fu and ken, but this distinction was abolished after the war, and the two types of prefecture are now functionally the same.

The prefectures are also often grouped into eight regions (Chihō). Those regions are not formally specified, they do not have elected officials, nor are they corporate bodies. But the practice of ordering prefectures based on their geographic region is traditional.[1] This ordering is mirrored in Japan's International Organization for Standardization (ISO) coding.[5] From north to south (numbering in ISO 3166-2:JP order), the prefectures of Japan and their commonly associated regions are:

Note: Due to the division of Korea, Kōgen (Kangwon/Gangwon) and Keiki (Gyeonggi) are divided between North Korea and South Korea. While each Korea has its own Kangwon/Gangwon Province, the North Korean portion of Gyeonggi has been absorbed into other provinces.